Device for phase modulation



April 24, 1951 D. ZSCHOKKE DEVICE FOR PHASE MODULATION Filed March 23,1948 ou/pul 1W vs/vro/e DIE Tf/ELM Zsc HOK KE 5y %AM/ ATTOR E Y PatentedApr. 24, 1951 DEVICE FOR PHASE MODULATION *D iethelm Zschokke,Solothurn, Switzerland, assignor to Autophon Aktiengesellschaft,Solothurn, Switzerland Application March 23, 1948, Serial No. 16,512

In Switzerland April 3, 194'! 4 Claims.

Circuits are known which enable to modulate the frequency of analternating voltage by modulating its phase, the instantaneous phaseshift being in advance with a positive modulating voltage and inretardation with a negative modulating voltage with respect to thecarrier frequency.

For communication purposes, it is desirable to applyphase departures of800 or more angular degrees, 1. e. the instantaneous advance orretardation of phase should total up toseveral periods. The technicalmodulation methods known up to now do not enable to produce directlysuch considerable shifts. Known modulation circuits enable phasedepartures, of i45 or i90. Bridge circuits are also known enabling toproduce a phase departure of i180, i. e. a

' complete cycle. In order to obtain phase departures of several hundredangular degrees, a low carrier frequency is used, such frequency beingmultiplied after modulation, the phase departure being then increased inthe same proportion. A peculiarity of known arrangements for phasemodulation is that their circuit may'not be loaded at all orto a verysmall extent.

The present invention relates to a device with loadable circuits and in.which a maximum phase departure of a complete cycle is obtained. r

The invention relates to a device for phase modulation and it ischaracterised in that the input voltage, constant with respect tomagnitude and frequency, is supplied to an oscillating circuit which iscoupled with two other oscillating circuits, one of which comprisesavariable re actance controlled by the modulating voltage and whichvaries the voltage, induced in this circuit, in function of themodulating voltagejand,

in that in the other circuit such a back voltage, also constant withrespect to magnitude and frequency is induced by the input voltage thatin circuits connected in series appears an output voltage which isconstant with respect to magnitude and the phase shift of whichwithrespect to the input voltage is a function of the modulatingvoltage. Particularly, the phase modulation is obtained in that themagnitude of the back voltage amounts to half the resonance voltage inthe variable oscillating circuit and'in that it possesses a phase shiftwith respect to this resonance voltage of an integer multiple of 1r. Ifthe coupling of the variable oscillating circuit with the input circuitis loss-free and inductive or capacitive, the induced resonance voltagepossessesv a phase shift of i90 with respect to the input voltage. Inthe case of loss-containing coupling a phase shift different from 90 isobtained. Such phase shift'is of no moment for the purpose of phasemodulation. If such a device is loaded with an impedance at the output,a mutual influence of the coupled oscillating circuit follows which may,however, be compensated by introducing a further impedance. This makesthe device loadable to a large extent. The maximum phase departureobtainable with the device is 11802 i. e. a complete cycle. v

An executional form of the invention isexplained, by way of example,with reference to the drawing. I v 1 illustrates the coupling of a fixedand of a variable oscillating circuit.

Fig. 2 shows the corresponding voltage. vector diagram. V

Fig. 3 shows the tapping of a back voltage in a device according to Fig.1.

Fig. 4 shows the vector diagram of the com-l bined voltages.

Fig. 5 shows a device for phase modulation with three coupledoscillating circuits.

Fig. 6 shows the compensation of a mutual infiuence of the coupledcircuits according to Fig. 5 due to a load impedance.v

Fig. '7 shows the vector diagram, in caseof a loss-free coupling of thecircuits.

In Fig. 1 is represented the coupling of two oscillating circuits K1 andK2. A voltage Veconstant with respect to magnitude and frequency. issupplied to the fixed oscillating circuit K1. The oscillating circuit K2comprises a variable reactance. V i

Fig. 2 shows the corresponding vector diagram. If the oscillatingcircuit 2 is tuned to resonance, a voltage Vvo is induced, the phaseangle (p0 of which is with respectto the input voltage Ve. If thereactanceof the oscillating circuitKz is varied and thus the oscillatingcircuit de-tuned, the magnitude and phase of voltave Vv is altered andthe tip of the voltage vector travels over a circle in a known manner.If the reactance is variable between and +9 a variable phase shift 'from0 to is obtained with respect to the input voltage Va.

In order to obtain a phase departure of 360", the variable back voltageVv is combined with the fixed back voltage Vr, as shown in Fig. 4. Thisfixed back voltage possesses with respect to the variable voltage Vvo atresonance a phase shift equal to an integer, multiple of 1r, i. e. aphase angle 0 or 180 and the magnitude of voltage V: is equal to half ofthe voltage vvo- If the voltages Vr and Vvo are in phase, the voltage V:is subtracted from Vvo, if said voltages are in opposite input voltageVa is supplied, the resistance being-1 connected in series with theoscillating circuit K2. The back voltage Vr may also=be tappedfrom anoscillating circuit K which iscoupled in a fixed manner withtheoscillating: circuitKi, the oscillating circuits K2 and IQ beingconnected in series in suitable phase relation. The fixed input voltageVa is preferably"being-produced in a known way, by means of a quartzgenerator.

The oscillating circuits K2 and K3 arecoupled,

with the oscillating circuit K1 in a fixed man- In the a able.oscillating I circuit.- Kzr n1 ef= erably the capacity: ifsbeing varied;Particularly, the. variation, of the, oscillating circuit may be,Qbtainedby means of a. controlled reactanceas explained. f r m le. he,U. Anatent an- Pl ea n. Ser. No. 132.252.. fi ed ar h 94. andtc whichthe ow frequency modul t n ag is supplic Then. i the. controlled. reac ace varies the induced voltage. in; functionoi themed lat n volta e.

f. the. dev ce ac ording. t E g. 5 is. l aded a theo'ut'putwith animpedance Za (Fig.5); a.rr ru tealv nfiu ncecf the twe sciflating. ciruits ta p hrou h such; ceup in Suc nfluence i being. cnmensatedf byconnectin half; th voltage of selfinduction'lis with the oscillatingcirc lt a s cond i pedance Zaf being ar an in theoscillating circuit;Thisj'enables to obtain a dev ce. whi h. is oa able: a wilt i hin awidrange. It has been found convenientto arrange the self nduction. oils ofthe hr e os i a in ts n a cylinder. hee elf: n uc on 1 be.- arranged m vbly between he o fixed, co 2: a d chis en les a v ry p ec e i tment" ofphase-relation between the back voltage of oscillating circuit, K; and"the resonance voltage in the variable oscillating circuit K2.

The oscillating circuits-Ki, K2 andKa may, insteadofbeing-of a purelyinductivenature; be coupled in a differentway: If, for example; theoscillating circuitsili'z= and K3 are coupled to the oscillating circuitK'i over imped'ances; the phase angle goo of the resonance voltageVvowith respect to the input voltage V willbe no'more 90", but any angle;The coupling of circuit K to the oscillating circuit 1 K; has) to bedonein; such a mannerthat the voltage induced in circuit 3 possesses thesame phase relation with respect to, the vel aeea he; re 'c teevqinfluence on any disadvantageousacti'on on the phasemodulation isbeing'produced by such phase relation.

What]? claim is? 1; In' a device for phase modulation, a firstoscillating circuit, a lead-in means for the input voltage to said firstoscillating circuit, a second oscillating circuit, a third oscillatingcircuit, said second and said third oscillating circuits being coupledwith said first oscillating circuit, a variable reactance in said secondoscillating circuit, saidreactance being controlled 1 by the. modulatingvoltage; and said second and saidthird oscillating circuits being seriesconnected.

2. In a device for phase modulation, a first oscillating circuit, alead-in means for the input voltagetosaid first oscillating circuit, asecond oscillatingcircu t a third oscillating circuit, said second and,said; third oscillating circuits being coupledwitli said firstoscillating circuit, a variable capacitance in said second oscillatingcircuit," said; capacitance being controlled by the modulating voltage,and said second and said third. oscillating circuits being seriesconnected.

3. In a device for phase modulation, a first oscillating circuit, valead=in means, for'the input voltage to said first'oscillating,circuit,.a second oscillating.- circuit, althirdv oscillating circuit,said second and. said third oscillating. circuits being coupled, withsaid' first. oscillating circuit, a var.- iable. capacitance inisaid.second oscillating circuit, said capacitance. being controlled by themodulating. voltage and said, second and. said third oscillatingcircuits being series connected, acon ectionbetween the middle. of, theinduct; ance 0i sa d; third oscilla ing, ircuit and aid c nd s lat ng.ir uit... afirst impedan a he utput or. the seriesv connection oisaseeendiwith' said hird oscillating ir uit. an a cond mp dance in said,third. o cillatin circuit;

n a device for hase modula on. a fi t sc llatin ircuit. l adn mea s. forh i p voltage to said first oscillating circuit, a second scil ating ciuit. a third" os illat na rc t d second and" said third oscillatingcircuits being coupled with said first oscillating. circuit, a variablereaotance included in said second oscillating circuit; said reactancebeing controlled by the modulatingvoltage, and said secondand said thirdoscillatingcircuits being series connected, a coil included in each ofsaid three oscillating circuits and; forminga part of said circuits,said three oscillating, circuits being inductively coupled with oneanother by means of' said coils, the coil of the first oscillatingcircuit being adjustably arranged with regard to the coils of the twoother oscillating circuits.

DIETHELM ZSCHOKKE.

REFERENCES CITED The. following references are of record in the filecithis. p tent:

UNITEDv STATES Number Name Date 2,374,810 Fremlin May 1, 1945 2,430,126Korman Nov. 4, 1947 2,436,834 Stodola Mar. 2, 1948 2,461,307 Antalek'Feb. 8, 1949

